It's disappointing that the auction didn't disclose the need for airbags and tensioners. I'd go back to them, and try to get out of the sale. You're going to have more into the repair in parts, than what the auction price probably was.
However, I've had both seats out of the car, and torn down to the frame. There is a seat belt tensioner on the outside of the seat that connects via cable to the seat belt buckle. If these have blown, they might be accessible with the seat in the car, but it could be difficult. See the pictures in my heated seats thread in my signature. Or google "Adding heated seats to LT"
If the seat belt does not retract into the A-Pillar there are explosive pretensioners in the front on each seat belt. When doing the seats I spent some time on Youtube, and there's a video of a Cruze replacing these a-Pillar devices.
Then the main Air Bag controller is behind the console in the front. That may have to be reprogrammed. I had both front seats and the center console completely out of the car to do the heated seats.
The seats at a recycling center were $300-$500 each. this is because each seat contains an airbag, and a seat belt tensioner. While they can be removed from the seat, I'm guessing most shops are selling the entire seat, and not dealing with the disassembly.